Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities

Kobingi Nyakeya *

Kenya Marine and Fisheries Research Institute, Baringo Station, P.O. Box 231, Marigat, Kenya and Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.

James Onchieku

Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.

Frank Masese

Department of Fisheries and Aquatic Science, University of Eldoret, P.O. Box 254, Eldoret, Kenya.

Zipporah Gichana

Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.

Albert Getabu

Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya.

Jane Nyamora

Department of Environment, Natural Resources & Aquatic Sciences, Kisii University, P.O Box 408 -40200, Kisii, Kenya and Kenya Marine and Fisheries Research Institute, Mombasa Headquarters, P.O. Box 81651 – 80100, Mombasa, Kenya.

*Author to whom correspondence should be addressed.


Abstract

Aims: To determine the spatial variation in physico-chemical water quality attributes in estuarine ecosystems of South Coast Kenya to inform its management.

Study Design:  We employed diagnostic research design where such factors as anthropogenic activities, hydrology, and accessibility were considered in choosing 12 sampling stations. A mixed sampling design (probability and non-probability) was used to sample.

Place and Duration of Study: Four discharging rivers into estuarine system with a reference point were identified. 12 sampling points were earmarked and sampled for 12 months.

Methodology: Nine selected water quality parameters were collected in triplicates monthly for 12 months. Temperature, dissolved oxygen, pH, conductivity, salinity and TDS were collected in situ using YSI Multiparameter meter (Professional plus) while nutrients were analyzed in the laboratory calorimetrically. Data was tested for normality and homogeneity of variances using Levene's and Shapiro-Wilk tests. Two-way analysis of variance (ANOVA), and Principal Component Analysis (PCA) were done using the 64-bit R Software version 4.3.0 to test for significant differences and correlate the parameters among the sampling sites respectively. Observed differences were considered statistically significant at P < 0.05.

Results: The measured environmental variables differed significantly among the sampling stations (P < 0.05). temperature and salinity exhibited moderate to strong effect on water quality, while pH and nutrients (phosphates, nitrates, and ammonia) exhibited mixed effects with both negative and positive loadings on the Principal Components. It is demonstrated that the south coast estuary, Kenya is affected by two gradients: mineralization from the sea and the organic matter gradient at the upstream stations dominated by the fluvial inflows from the respective rivers.

Conclusion: The south coast of Kenya estuary is impacted by natural processes and anthropogenic activities. we recommend for continued regular water quality assessment and monitoring to acquire sufficient data to shape policy frameworks towards its sustainable management.

Keywords: Pollution, water quality, Western Indian Ocean, estuarine systems, anthropogenic activities, south coast Kenya


How to Cite

Nyakeya , K., Onchieku , J., Masese , F., Gichana , Z., Getabu , A., & Nyamora , J. (2024). Trends in Water Quality in a Tropical Kenyan River-estuary System: Responses to Anthropogenic Activities. Asian Journal of Biology, 20(6), 34–51. https://doi.org/10.9734/ajob/2024/v20i6413

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